Here's one of the major reason's why data may not leak. Physical networks to/from are nonexistent making routing of any and all communications to/from potential secret installations heavily controlled. https://www.pilotfiber.com/blog/antarctica-internet There's also one way in and out if you're duty station involves such complexes. Snowden lived in Hawaii at the time, making things a bit easier to smuggle equipment containing what he offloaded. In Antarctica, your transport is via boat or plane through gov contractors with probably rigorous inspections in and out. Very akin to what you'd find in installations like area51. When looking into, I do remember reading about alcohol/drugs being forbidden but there is a thriving black market. Maybe all the countries down there are just researching penguin farts and looking at rocks but if there's more than than there's a way and established method to keep it secret.